Virtual Vista science 20 Unit A chapter 1-2 conclusion

Solutions

homogeneous mixture (two or more substances distributed) where the solute and solvent are not visible. Often liquid, but can be solids. Gasses are liquid in a different form.

Solute

a substance which bonds are broken by a solvent; minor part of solution, and what gets dissolved.

Solvent

greater proportion in the mixture, breaks down solutes bonds.

Physical properties

conductivity, colour, hardness, flexibility

Chemical properties

how composition of matter changes, or how it reacts chemically

Element

pure substance that cannot be broken down simpler by chemical means

Atom

smallest part of an element that has all of its properties

Proton

positively charged particle in nucleus of an atom

Neutron

neutral particle in nucleus of an atom

Electron

negatively charged particle outside atoms nucleus

Atomic number

the number of protons inside atom’s nucleus

Atomic mass

average mass of an elements particles; protons, neutrons (not electrons, barely hold weight)

Mass number

The total count of protons and neutrons in a specific isotope of an element (because isotopes of an element have a different amount of neutrons than the base element) . Since atomic mass is closely related to the mass number, you subtract atomic mass by atomic number, and round up for the most common neutron count

How to find the number of neutrons in an atom?

For an exact count of neutrons of an isotope: subtract the mass number (sum of protons + neutrons) by the atomic number (protons)

—But because the mass number is of the most common isotope, and often close to the rounded atomic mass (which reflects the average total weight of all isotopes)—

For a rough estimate of the most common isotope: round atomic mass (total weight of atom) to nearest whole number and subtract by the atomic number (protons)

Do protons and neutrons compose most of an atoms volume?

While its true they compose most of an atoms mass, they are not most of the volume, as they are located in the nucleus, a tiny spot in the middle of the atom.

Electron cloud

A term used to describe the space outside the nucleus within the atom where electrons reside. The term "cloud" comes from the rapid, unpredictable motions of electrons within orbital paths around the nucleus.

Why are electrons bound to the nucleus?

Oppositely charged objects are attracted to each other

How do atoms not repel each other if they both have a surrounding negatively charged field

Although they may initially repel, the large concentration of positive charge in their nuclei prove to be a stronger attracting force, both pulling the other atoms electron cloud simultaneously.

Quarks

the extremely tiny particles that make up protons and neutrons

Energy level

specific region outside of nucleus available for electrons. Only a certain amount of electrons are able to occupy an energy level. The level closet to the nucleus have the least amount of energy, and are filled first, with the others following in ascending order.

What is all matter made up of ?

A large number of associated atoms. The proton, nucleus, and electrons of an atom determines how it bonds with other atoms. These bonds determine physical and chemical properties of their respective substance. The structure of atoms interacting within a substance determine if it shines, is soft/rigid/ or can conduct energy.

Label the terms

electrons are equal to the number of protons (atomic #) in a stable atom

+1 positive and -1 negative contribute to a neutral charge: 0.

How many electrons fill each energy level?

from the 3 energy levels of an atom, 2 maximum fit in the first layer, and 8 in the second and third layers.

Valence electrons

Electrons on the outermost energy level

What is the transfer of electrons when a metal is in the equation?

Metals usually lose and become cations, while nonmetals “steal” the electron to become negatively charged anions.

ion

a charged atom. Anytime an atom is not balanced in charge— no longer stable— it becomes an ion. Non-metal takes on suffix ‘-ide’. Unless, the non-metal is a molecule with a whole (-) or (+) charge (polyatomic ions— diff from atoms bonding w/ each other), it takes on ‘-ate’.

ex: oxygen gains 2 electrons: oxide ion

phosphate (phosphorus and oxygen molecule with negative charge) bonds with aluminum: aluminum phosphate

tl/dr:
non-metal ion: ‘ide’
non-mental polyatomic (charged molecule): ‘ate’

Cation

positively charged ion

Anion

negatively charged ion

What are the number of valence electrons and tendencies for Alkali metals, Halogens, and noble gasses?

• Alkali metals (group 1): 1 valence electron; highly reactive, as they only need to lose one electron to form a stable bond

• Halogens (group 12, reactive non-metals): 7 valence electrons; highly reactive— only need to gain 1 to form a stable bond

• Noble gasses (group 8): 8 valance electrons (helium has 2); inert, rarely form compounds due to a full valence shell.

Why do elements in the same group share similar chemical and physical properties?

Because they tend to gain, lose, or share electrons in a predictable manner— due to the same amount of valence electrons.

And because bonding behavior affects melting point, boiling point, conductivity, and solubility.

Ex:

Alkali metals are all soft, low-density metals with low melting points due to their weak metallic bonding (tending to only form a single electron bond).

What are the characteristics of the 3 groups?

• Alkali: soft, highly reactive metals that form strong bonds w/ water

• Halogens: non-metals who have strong attraction for outside electrons, form salts w/ metals

• Noble gasses: gasses w/ low reactivity

.

.

Each group follows similar periodic trends, such as increasing in atomic weight and reactivity as you go down the column (except noble gasses, remain mainly unreactive.)

Difference between Bohr and the Electron Dot model of an atom?

Bohr: shows all electron levels

Electron dot: only shows the valence electrons

What is the importance of the valence shell

When two atoms are in proximity, both nuclei’s positive charge attracts the (-) charged electron clouds. The outer-shell electrons are the significant electrons in this process. How an electron loses or gains (bonds) is determined by the valance. Atoms with similar #’s of valence electrons have similar bonding properties.

Why is reactivity gauged by the valence shell electrons?

Atoms crave to be stable (can have balanced charges and not be stable), and to have whichever one of its energy layers is the outermost full. They tend to take the path of least resistance, where if the choice is to either gain 7 or lose 1 to have a full layer, they would lose 1.
i.e atoms closer to a full shell will more readily gain/lose

Note: by losing this electron, the atom is now stable, but it has more protons than electrons giving it a positive charge; cation.

bond

electrostatic forces keeping atoms or ions together. When bonds form, the full compound is neutral and stable.

Covalent bond

Bond between non-metals where two atoms share electrons to fill each others shell. Imagine the energy layers overlapping, and the electron(s) passing around both atoms.

Molecule

• Molecule: A group of two or more non-metal atoms held together by covalent bonds, forming a discrete, stable unit.

  • Molecules have lower melting and boiling points than ionic compounds, are generally flammable, softer, less soluble in water, and do not conduct electricity.

  • For example:

    • CO₂ and C can react to form a new molecule (e.g., CO).

    • CO₂ and O₂ can react to form new compounds (e.g., CO or O₃), but not by merging whole molecules together.

  Key idea: When non-metals bond covalently, they form molecules. However, molecules themselves do not usually bond to each other as intact units. Instead, their bonds must break and atoms are rearranged to form new molecules.
  You can think of a molecule as a kind of “final product”—stable unless energy is added to rearrange its atoms.

BrINCLHOF twins

non-metals so reactive, they form bonds with themselves. Br₂I₂N₂CL₂H₂O₂F₂

Metals tend to lose and non-metals tend to..?

Gain. Non-metals, with the exception of noble gasses, require 1 or more electrons to be stable. Metals require losing 1 or more electrons to be stable.

Molecular compound

A compound composed of identical molecules, typically formed by nonmetals. For example, a bucket of water is just many H₂O molecules coexisting. These molecules are held together by intermolecular forces, not any concrete bonds (inter: between two or more, intra: within).

The molecule “H2O” would be one unit of this structure. Due to the fact there is a single type of molecule within, the structure is a pure substance.

• Network covalent solids are the expectation to this, where they are, as a whole, made up of covalent bonds—the whole structure is the fundamental unit (debated as molecule).

How do ionic compounds differ from molecular compounds fundamentally?

Unlike molecular compounds, which can be funneled into a single molecule part, ionic compounds only bond as a lattice structure. Ionic compounds, by contrast, do not have standalone “units”—forming as a lattice structure from the instant they are created. They follow a fixed ratio of ions (e.g., Na⁺:Cl⁻ in NaCl), and that ratio simply scales across the entire structure. The formula unit represents the lowest whole-number ratio of ions in this lattice, but it’s not a physically separable particle like a molecule—only a picture of the simplest repeating ratio w/in the structure.

Ionic bonds don’t break into molecule-like fragments. Instead, they dissociate into individual ions. Their identity lies in the crystal lattice—not in any isolated unit.

i.e molecules can chill, and come to form a structure if they so please, but ionic bonds have no base unit and are lattice structure till death

Molecular formula

chemical formula displaying of many atoms of each element a molecule contains

i.e Ethane: C₂H₆ , which means it has 2 carbon and 6 hydrogen

How do continuous strand molecules work?

C has 4 valence electrons. It must either gain 4 or lose 4 to be stable.

H has 1 valence electron in the first layer. It must gain 1 to be stable.

C and H can share 1 electron to balance out, but while H is stable, carbon must either balance out with more hydrogen or other carbon.

This can create a chain of numerous carbon, which finally ends on a hydrogen

Metallic element, Ionic compound, molecule

1. metal with metal (metallic)

2. non-metal with metal (ionic)

3. non-metal with non-metal (molecular)

Lattice structure

the crystalline shape ionic bonds take on when forming ionic compounds.

bonding within a Metallic element

Ex:

The individual Aluminum atoms (Al) crave stability, so they take the path of least resistance and lose (moreso “shed”) 3 electrons. The atoms are now positive ions, cations, and those electrons are ‘delocalized’ (free moving). The aluminum cations are then held together by their mutual attraction to this "sea" of free electrons.

• The metal as a whole remains electrically neutral, since the number of free electrons matches the number of protons.

• This is why metals are conductive, the electrons move around freely, and electric current flows as energy jumps from electron to electron within the mobile sea.

Characteristics of ionic compounds?

Generally high melting point, and can conduct electricity when melted or dissolved in water (The dissolved ions float around and allow current to flow)

How do ions attract each other?

ionic bonds involve a transfer of electrons, so one atom becomes (+) and the other (-). The two oppositely charged ions attract each other after becoming charged.

Bond strength

how much energy it takes to break bonds apart

Are ionic bonds or molecular bonds stronger?

Individual covalent bonds between atoms, like C-C, are harder to break apart, although intramolecular bonds are generally easier to break apart.

While ionic bonds on there own are weaker, the lattice structures as a whole are stronger than molecular compounds.

How is melting point related to bond strength?

Heat energy moves atoms/molecules apart. The more energy required (higher heat) means a stronger bond.

Are molecular or ionic compounds stronger at room temp?

At room temp, molecular compound strength varies; gas, liquid, solid, but generally melt lower— weaker intermolecular bonds.

At room temp, all ionic compounds are solid— stronger bonds

Are there more metals or non-metals on the periodic table?

There are more metals.

The orange blocks are non-metals.

Evidence of chemical change?

• Colour change

• Change in state; gas or precipitation is produced

• odour (gas is produced)

• Change in energy (heat expelled or absorbed)

  • Exothermic reaction (expels heat/light; candle, glowsticks)

  • Endothermic reaction (absorbs heat; ice pack, cooking egg)

What happens to ionic compounds when broken down in a solution?

The charged ions are made free to form new bonds with other substances in the solution (or just chill).

What is the general process from atom to molecular or ionic compound?

Atom :_{covalent bond} atom → molecule

Molecule : molecule → molecular compound

---

Ion⁺ :_{electrostatic bond} Ion^- → ionic compound/ lattice structure

What’s so special about water that it is considered the ‘solvent of life’?

an H20 molecule is ‘polar’ meaning it has a negative end and a positive end. It has a partial negative charge (1^- oxygen atom), and a partial positive charge (2⁺ hydrogen atoms) at the bottom of the oxygen.

How do water molecules break down an ionic compound?

1. The oppositely charged ions are held together in a lattice structure.

2. the positive side of the H2O pulls out the anions

3. the negative side of the H20 pulls out the cations

How do water molecules break down a molecular compound?

Since molecules (atoms held together by covalent bonds) are neutral, the H2O cannot break molecular compounds into individual atoms.

What they can do, is separate the molecules with uneven charges in the compound, due to unequal sharing of electrons molecule to molecule.

Why are dissolved ionic compounds conductive (electrolytes)?

The anion and cations are free moving, therefore can complete the circuit if positive and negative electrodes are placed within the solution.

The ions can carry the charge from one electrode to the other. Their movement creates the current.

Why are dissolved molecular compounds not conductive?

While molecular compounds can be broken up by targeting parts of uneven charge, the molecules will always have an equal number of electrons and protons, therefore neutral, and not able to carry current.

The particles generally stay in molecule form.

concentration

the amount of solute compared to the amount of the whole solution (including the solute).

One form of determining concentration is as follows:

10g salt in 90g water

concentration is (10/100) or 10% salt by mass

concentration (when naming solutions)

a solution with alot of solute; high ratio of solute to solution

dilute

solution with little solute; low ratio of solute to solution

Can a solute, and subsequently a solution, be unintentional?

Yes, PCBs or pollutants can be present in water

What are 5 properties that indicate relative concentration:

• colour

• taste

• odour

• colour intensity

• transparency

What is one way to test concentration?

If solution is electrolyte, do a conductivity test→ more movement, higher charge(?). The rate of reaction can give a relative amount of concentration; more concentrated react more quickly.

qualitative properties

basic attributes you can observe with one or more of the 5-senses

What do chemical reactions involve between ions, atoms, and molecules?

collisions

collision reaction theory

if particles collide with a certain amount of energy, and a certain orientation, then the particles will be rearranged. The result is the chemical reaction.

When molecules collide, they may be broken into individuals atoms, and recombine in different arrangement forming new molecules.

Atoms move faster in liquids/gas than in solids.

Why do higher concentrations react more quickly and more strongly?

if there is higher concentration, there will be more possible collisions, and more possible chances for collisions

There are many ways to describe concentration, what are 3?

1. percent by volume (%v/v): ‘mL of solute / mL of solution * 100%’

   • volume of liquid solute dissolved in total volume of solution

2. parts per million (ppm): ‘g of solute/g of solution * 10^6 ppm’

   • used to describe levels of substance in very dilute aqueous solutions

3. molar concentration (molarity): ‘mol of solute(n)/L of solution(v)’ or ‘c=n/v’

   • amount of mols in total volume of solution

   • partitive division, how many mols spread out across x amount of total solution

what is the molar mass formula?

M=n/m

M= molar mass (atomic mass of the atoms)

n= mols of solute

m= mass in g

can be rearranged.

How would you rearrange the mol concentration formula to find mols?

c = n/v

n is “mols of solute”, isolate n

n= cv

Does dilution change the number of moles in a solution?

Dilution occurs when more solvent is added to a solution, this does not change the amount of solute. Although, it does change the concentration.

i.e solute = same, solvent = increase , change in solute/solution ratio

standard solution

solution of very accurately known concentration, that is diluted to make other solutions.

What is the dilution formula

c₁v₁=c₂v₂

C1= initial concentration

V1= initial volume

C2= final concentration

V2= final volume

to find dilution, you find the values that make this expression true through algebraic means

When to use dilution equation and molar concentration calculation?

Use the molar concentration formula when you’re starting with a solid solute.
Use the dilution equation when you’re starting with a solution and changing its concentration by adding solvent.

What does ‘aqueous’ mean?

The solution was formed with water as the solvent.

When to use each formula?

• PPM: very small concentrations, identify mass of solute in (g), and volume of solution in (L)

• Molar concentration: finding molarity, or number of moles in a solution.

• Percent by volume: concentration of liquid-liquid solutions

• Dilution equation: when changing concentration (not amount of solute) by adding/removing solvent

All can be rearranged to find missing variables.

What are some things to remember when balancing atomic equations

1. The coefficient will multiply by the subscript; 2O₂ means 4 oxygen in total

2. For brackets, the coefficient will apply to each; 2Ag(NO₂) means 2 silver, 2 nitrogen, and 4 oxygen

3. balancing is just ensuring both sides have the same amount of compounds

How to find subscripts from compound names?

Look at ‘hydrogen sulfide’ for example. We know that when forming bonds, sulfur takes on the charge of -2, or tends to gain two electrons to be stable.

Hydrogen takes on the charge on +1, or tends to lose one electron to be stable.

The path of least resistance for this compound garners 2 (+1) hydrogen for 1 (-2) sulfur. Therefore:

H₂S (g)

What do coefficients represent?

Think of coefficients as moles, representing the ratio between amount of substances.

example:

in H₂ + O₂ → 2H₂O

What’s the ratio ratio of O₂ to H₂O ?

O₂ has the coefficient 1, H₂O has the coefficient 2

1:2 mole ratio.

for every one O₂ molecules, 2 moles of H₂O are formed

Conversion factors

Because coefficients represent mole ratios, you want to find, say how many moles of Fe will react with 0.27 mols of O₂ molecules:

mols given * coefficient of desired / coefficient of given = mols of desired

For example:

0.27 × 4/3 = 0.36

there is a 3:4 ratio between oxygen and Iron, for every 3 mols of oxygen, there will be 4 mols of iron. Since there is less than 3, you scale down.

Scaling down works by taking the given amount of a substance, determining what fraction it is of the original ratio, and applying that same fraction to the other substance to maintain proportionality.

Why is it important to look at the non-metal when deriving chemical formulas from names?

The non-metal gains electrons, so to streamline the process, you can determine how many electrons it needs from the metal.

How does ionic bonding work?

metal to non-metal bonds, or ionic bonding, is unique because of how metals are made up of positively charged particles within a ‘sea’ of floating electrons.

Occasionally some free floating electrons are lost to other atoms, which upsets the balance. The electrons are usually lost to atoms with a stronger affinity for them. The atoms receiving the electrons become negatively charged, and attract the positive ions from the metal.

oxidation

loss of electrons

example of a half reaction:

Ag(s) → Ag⁺(aq) + 1e^-

reduction

gain of electrons

example of a half reaction:

Ag⁺(aq) + 1e^- → Ag(s)

refinement; purifying metals from compounds

process of purifying metals from their compounds. Say in the case of Ag₂S(aq), reduction is used to give the metal, Ag+, its electrons back, breaking the ionic bond. The neutral Ag compounds form metallic bonds thus creating pure silver.

spectator ion

the ion that does not undergo chemical change

Reduction agent

One that loses electrons

Oxidizing agent

One that gains electrons

What is the relationship between the most stable atom and the most reactive ion?

The most stable atom has the most reactive atom and vice versa.

Between an atom and ion, if the ion is above the atom, meaning it is more reactive to gaining electrons, while the atom is more reactive to losing electrons, there will be a spontaneous reaction.

Between an atom and ion, if the atom is above the ion, meaning it is more stable, less likely to oxidize, while the ion is also stable, less likely to reduce, there will be a non-spontaneous reaction.

spontaneous

requiring no outside energy for a chemical reaction to occur

non-spontaneous

requires outside energy for a chemical reaction to occur.

single replacement

The switching of an ion in and out of a compound, and can only occur if the ion being switched is more reactive than the current ion.

Ag₂S + N → Ag₂N + s

*probably not accurate

galvanic/voltaic cells

devices that use a chemical reaction to create energy (reduction oxidation)

How does a galvanic/voltaic cell work?

Say copper and zinc are your electrodes. Cu ions are more reactive than Zn atoms are stable, therefore Zn has a weaker pull for electrons, enabling the stronger attracting force: Cu to take them.

We have a solution of ZnSo₄ and CuSo₄ in the respective electrodes containers to balance the equation with So₄^- ions. They also serve to provide a steady supply of Cu⁺ ions to start off the reaction by attracting Zn(s) electrons. The ZnSo₄ provides a place for the Zn²⁺ ions to go after oxidizing (losing electrons).

the movement of Zn electrons constitutes an electrical charge.

Without a salt bridge, the Zn(s) atoms will keep losing electrons, becoming Zn⁺ ions, and detaching from Zn(s) to float in the ZnSo₄ solution. The opposite will occur for Cu, as the Cu²⁺ ions will use zincs electrons to become neutral and bond with Cu(s), forming a bigger piece of copper.

Metallic bonding occurs between neutral metal atoms.

oxidation half reaction: Zn(s) → Zn²⁺+ 2e^-

reduction half reaction: Cu²⁺ + 2e^- → Cu(s)

Cathode

The electrode which undergoes reduction.

Anode

The electrode which undergoes oxidation.